Ngamjarus C, Pattanittum P, Somboonporn C. Roselle for hypertension in adults. Cochrane Database Syst Rev. Jan 20, 2010;(1):CD007894.
The reviewers included randomized controlled trials (RCTs) with durations of 3-12 weeks that compared hibiscus to a placebo or no intervention. The inclusion criteria required that the RCTs include patients over the age of 18 with systolic blood pressures (SBP) and diastolic blood pressures (DBP) equal or greater to 140 mm Hg and 90 mm Hg, respectively. The primary outcome measures were changes in the trough and/or
In June 2009, the authors searched the following databases for relevant articles: the Database of Abstracts of Reviews of Effectiveness (DARE), Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (2005-2009), EMBASE (2007-2009), Allied and Complementary Medicine Database (1985-May 2009), CINAHL (1982-2009), BIOSIS (1969-2008), AGRICOLA (1970-May 2009), Food Science and Technology Abstracts (1969-June 2009 week 1), International Pharmaceutical Abstracts (1970-May 2009), and International Bibliographic Information on Dietary Supplements (IBIDS). They also used other information resources, including www.clinicaltrials.gov, the System for Information on Grey Literature in Europe (OpenSIGLE), ISI Web of Knowledge, and hand searches of journals, conference proceedings, and reference sections of published articles. The final search was in September 2009.
Out of 159 records recovered in the literature search, 26 were retrieved for review. Of those 26, 17 were duplicates. The authors excluded two articles that did not include hypertensive patients, one report that was not an RCT, and one paper that was an initial report of another article. None of the remaining five articles met the inclusion criteria. Among these, one used black tea as the control in hypertensive diabetics,1 two used ACE inhibitors as controls,2,3 and the other study used as a control "ordinary" tea and only lasted for 15 days.4 An abstract of a randomized, double-blind, placebo control study of 6 weeks duration with pre- and mildly hypertensive subjects was not included because the complete article had not yet been published, but it has become available in its final form in 2010.5 All five of these studies found significant reductions in SBP.
According to the authors, "No reliable conclusions can be drawn about the benefit of
References1. Milot B. Antihypertensive effects of hibiscus in patients with type II diabetes. HerbClip. April 30, 2009. (No. 040191-375).
2. Minigh J. Efficacy and tolerability of hibiscus in patients with hypertension. HerbClip. February 28, 2007. (No. 100263-323).
3. Oliff HS. Study finds hibiscus extract may help control hypertension. HerbClip. February 28, 2007. (No. 020571-323).
4. Webb D. Hibiscus tea lowers blood pressure - clinical study. HerbClip. February 29, 2000. (No. 091399-171).
5. Oppel-Sutter M. Hibiscus tea may help lower blood pressure in mild hypertension. HerbClip. March 15, 2010. (No. 021066-396).